An apparatus comprising a micromachined (a.k.a. MEMS, Micro Electro Mechanical Systems) silicon flow sensor, a flow channel package, and a driving circuitry, which operates in a working principle of thermal time-of-flight (TOF) to measure gas or liquid flow speed, is disclosed in the present invention. The micromachining technique for fabricating this MEMS time-of-flight silicon thermal flow sensor can greatly reduce the sensor fabrication cost by batch production. This microfabrication process for silicon time-of-flight thermal flow sensors provides merits of small feature size, low power consumption, and high accuracy compared to conventional manufacturing methods. Thermal time-of-flight technology in principle can provide accurate flow speed measurements for gases regardless of its gas compositions. In addition, the present invention further discloses the package design and driving circuitry which is utilized by the correlated working principle.